Systems and methods for detecting physical changes without physical contact

ABSTRACT

Systems and methods are provided for detecting and analyzing changes in a body. A system includes an electric field generator, an external sensor device, a quadrature demodulator, and a controller. The electric field generator is configured to generate an electric field that associates with a body. The external sensor device sends information to the electric field generator and is configured to detect a physical change in the body in the electric field, where the physical change causes a frequency change of the electric field. The quadrature demodulator receives the electric field from the electric field generator and is configured to detect the frequency change of the electric field and to produce a detected response. The controller, coupled to the electric field generator, is configured to output a frequency control signal to the electric field generator and to modify the frequency of the electric field by adjusting the frequency control signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part application of U.S. patent applicationSer. No. 15/418,328, filed Jan. 27, 2017, which claims the benefit ofU.S. Provisional Patent Application No. 62/287,598, filed on Jan. 27,2016. The entire contents of each application are incorporated byreference herein in their entirety as though fully disclosed herein.

TECHNICAL FIELD

This application relates generally to the technical field of monitoringsystems, and more particularly, to a monitoring system that detectsphysical changes without physical contact.

BACKGROUND OF THE INVENTION

The performance of a variety of monitoring systems may be affected bywhere a sensor or its parts are placed relative to a target (e.g., ahuman such as an adult, teen, child, or baby) that is being monitored.For example, certain monitoring systems may require a sensor to be inphysical contact with a target and may further require a part (e.g., apower or data cable) to be connected from a sensor to a monitoringdevice. There may be other circumstances in which the sensor might beused to detect changes in occupancy of a vehicle seat. In this case thesensor might also sense vital signs—e.g., pulse and/or respiration—of aseat occupant without direct physical contact.

Known monitoring systems require a sensor to be directly in contact witha target. For example, a traditional electrocardiogram (ECG) usesexternal electrodes to detect a patient's ECG signal. The externalelectrodes are located on the ends of cables and must be physicallyplaced on a patient and near the patient's heart. This oftennecessitates the use of conductive materials that may be inconvenient tohook up and use, especially for long-term monitoring of a relativelyactive patient. These devices have significant limitations. For example,the patient must be physically connected to the device. If the patientwants to leave his or her bed, the device needs to be detached from, andthen re-attached to the patient on his/her return, often by a highlytrained staff member. The inconvenience and the delays associated withsetting up such monitoring systems are also not well-suited formonitoring more active targets, for example, a baby in a crib or aperson driving a vehicle. Although there are monitoring systemsincorporated into devices such as wristbands and armbands they stilltypically need to be directly in contact with the target, and oftenprovide inaccurate information and limited functionality.

Accordingly, there is a need for a monitoring system that does notrequire a sensor to be directly in contact with a target. There is alsoa need for a monitoring system that can assist in the management of atarget's health, fitness, sleep and diet by monitoring physiologicalchanges in a person's body. There is further a need for a monitoringsystem suitable for long-term use that can sense changes in a target andprovide timely and appropriate diagnostic, prognostic and prescriptiveinformation.

SUMMARY

This invention includes systems and methods that allow detection ofphysical changes within a body without physical contact with, orattachment to, the body. A body is a mass of matter distinct from othermasses. Non-limiting examples of a body include, for example, a human'sbody, an animal's body, a container, a car, a house, etc. These changesmight be physiological events such as cardiac function in an animal orchanges in the properties of a bulk material such as grain in a silo.These changes could be dimensional changes such as those caused by thefunction of organs in an animal, or changes in the composition of thematerial such as water content in lumber.

A key feature of the measurement technique used in this instrument isthat the measurement may be done over an extended volume such that thechanges of multiple phenomena may be observed simultaneously. Forexample, sensing two separate but related physiological parameters(e.g., pulse and respiration) may be accomplished concurrently. Theregion sensed by this instrument may be changed by sensor element designwithin the instrument. A further extension of bulk sensing capability isthe opportunity to use sophisticated computer signature recognitionsoftware, such as wavelet-based approaches, to separate individualfeatures from the composite waveform.

This application relates to U.S. Pat. No. 9,549,682, filed on Oct. 30,2014, which is explicitly incorporated by reference herein in itsentirety. This application also relates to U.S. Pat. No. 9,035,778,filed on Mar. 15, 2013, which is explicitly incorporated by referenceherein in its entirety.

Disclosed subject matter includes, in one aspect, a system for detectingand analyzing changes in a body. The system includes an electric fieldgenerator configured to produce an electric field. The system includesan external sensor device, coupled to the electric field generator,configured to detect physical changes in the electric field, where thephysical changes affect amplitude and frequency of the electric field.The system includes a quadrature demodulator, coupled to the electricfield generator, configured to detect changes of the frequency of theoutput of the electric field generator and produce a detected responsethat includes a low frequency component and a high frequency component.The system includes a low pass filter, coupled to the quadraturedemodulator, configured to filter out the high frequency component ofthe detected response to generate a filtered response. The systemincludes an amplitude reference source configured to provide anamplitude reference. The system includes an amplitude comparison switch,coupled to the amplitude reference source and the electric fieldgenerator, configured to compare the amplitude reference and theamplitude of the electric field to generate an amplitude comparison.They system includes a signal processor, coupled to the low pass filterand the amplitude comparison switch, configured to analyze the filteredresponse and the amplitude comparison response.

Disclosed subject matter includes, in another aspect, a method fordetecting and analyzing changes in a body. The method includesestablishing an electric field around a desired area of detection withan electric filed generator. The method includes monitoring frequency ofthe electrical field with a quadrature demodulator. The method includesdetecting changes in the frequency of the electric field with thequadrature demodulator. The method includes monitoring amplitude of theelectric field. The method includes detecting changes in the amplitudeof the electric field with an amplitude reference source.

Disclosed subject matter includes, in yet another aspect, anon-transitory computer readable medium having executable instructionsoperable to cause an apparatus to establish an electric field around adesired area of detection with an electric field generator. Theinstructions are further operable to cause the apparatus to monitorfrequency of the electrical field with a quadrature demodulator. Theinstructions are further operable to cause the apparatus to detectchanges in the frequency of the electric field with the quadraturedemodulator. The instructions are further operable to cause theapparatus to monitor amplitude of the electric field. The instructionsare further operable to cause the apparatus to detect changes in theamplitude of the electric field with an amplitude reference source.

Disclosed subject matter further includes, in yet another aspect, asystem for detecting and analyzing changes in a body. The systemincludes an electric field generator, an external sensor device, aquadrature demodulator, and a controller. The electric field generatoris configured to generate an electric field that associates with a body.The external sensor device sends information to the electric fieldgenerator and is configured to detect a physical change in the body inthe electric field, where the physical change causes a frequency changeof the electric field. The quadrature demodulator receives the electricfield from the electric field generator and is configured to detect thefrequency change of the electric field generated by the electric fieldgenerator and to produce a detected response. The controller is coupledto the electric field generator and is configured to output a frequencycontrol signal to the electric field generator and to modify thefrequency of the electric field by adjusting the frequency controlsignal.

Disclosed subject matter includes, in yet another aspect, a method fordetecting and analyzing changes in a body. The method includesgenerating an electric field that associates with a body with anelectric field generator. The method includes detecting a physicalchange in the body in the electric field with an external sensor device,where the physical change causes a frequency change of the electricfield. The method includes monitoring and detecting changes in thefrequency of the electric field and producing a detected response with aquadrature demodulator. The method includes receiving, by a controller,the detected response. The method includes outputting a frequencycontrol signal to modify the frequency of the electric field associatedwith the body. The method includes modifying, by the electric fieldgenerator, the electric field associated with the body based on thefrequency control signal.

Disclosed subject matter includes, in yet another aspect, anon-transitory computer readable medium having executable instructionsoperable to cause an apparatus to detect and analyze a change in a body.The instructions are further operable to cause the apparatus to generatean electric field that associates with a body. The instructions arefurther operable to cause the apparatus to detect a physical change inthe body in the electric field, where the physical change causes afrequency change of the electric field. The instructions are furtheroperable to cause the apparatus to monitor and detect changes in thefrequency of the electric field and produce a detected response. Theinstructions are further operable to cause the apparatus to receive thedetected response. The instructions are further operable to cause theapparatus to output a frequency control signal to modify the frequencyof the electric field associated with the body. The instructions arefurther operable to cause the apparatus to modify the electric fieldassociated with the body based on the frequency control signal.

Before explaining example embodiments consistent with the presentdisclosure in detail, it is to be understood that the disclosure is notlimited in its application to the details of constructions and to thearrangements set forth in the following description or illustrated inthe drawings. The disclosure is capable of embodiments in addition tothose described and is capable of being practiced and carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein, as well as in the abstract, are for thepurpose of description and should not be regarded as limiting.

These and other capabilities of embodiments of the disclosed subjectmatter will be more fully understood after a review of the followingfigures, detailed description, and claims.

It is to be understood that both the foregoing general description andthe following detailed description are explanatory only and are notrestrictive of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects, features, and advantages of the disclosed subjectmatter can be more fully appreciated with reference to the followingdetailed description of the disclosed subject matter when considered inconnection with the following drawings, in which like reference numeralsidentify like elements.

FIG. 1 illustrates a system for detecting and analyzing changes in abody according to certain embodiments of the present disclosure.

FIG. 2 illustrates a transfer function of a quadrature demodulatoraccording to certain embodiments of the present disclosure.

FIG. 3 illustrates a waveform combining both respiration and heart ratesignals according to certain embodiments of the present disclosure.

FIG. 4 illustrates a system for detecting and analyzing changes in abody according to certain embodiments of the present disclosure.

FIG. 5 illustrates a process of detecting and analyzing changes in abody according to certain embodiments of the present disclosure.

FIG. 6 illustrates a quadrature demodulator according to certainembodiments of the present disclosure.

FIG. 7 illustrates a signal processor according to certain embodimentsof the present disclosure.

FIG. 8 illustrates a system for detecting and analyzing changes in abody according to certain embodiments of the present disclosure.

FIG. 9 illustrates an inductor-capacitor (LC) tank oscillator accordingto certain embodiments of the present disclosure.

FIG. 10 illustrates a process of detecting and analyzing changes in abody according to certain embodiments of the present disclosure.

DETAILED DESCRIPTION

The manner in which materials behave in an alternating current (“AC”)circuit usually is described in terms of the amount of energy stored inthe material and the amount of energy dissipated in the material on aper cycle basis. Energy storage occurs in both electric and magneticfields created by the current. Dissipation occurs in transformation, inthe material, of electrical energy into thermal energy, i.e., heat.These properties can vary over a wide range depending on the material.In many materials the properties are predominantly one type.

Dissipation in some materials may be attributed to the magnetic fieldproperties of a material and in other cases to the electric fieldproperties. In more general cases, both of these mechanisms are present.Because of this, there is a convention in which the magnetic fieldstorage properties and any related dissipation are combined in a vectorsum and called permeability. Similarly, the vector sum of the electricfield storage properties and associated dissipation is calledpermittivity. These vector sums are expressed as complex values in whichthe dissipation is the real component and field storage properties arethe imaginary component. In the present disclosure, the aggregatedchange in properties of a body are detected and quantified by measuringchanges in the body's electromagnetic properties.

Although the approach described here works by sensing changes in theelectromagnetic properties, i.e. changes in both electric and magneticproperties, in some applications the significant changes occur in onlyone set of properties. For purposes of further discussion, theinstrument in this invention detects changes in permittivity. Detectionof any other suitable property or combination of properties that areappreciated by a person skilled in the art is also within the spirit andlimit of the disclosed subject matter. The dissipative component ofpermittivity often is expressed as the loss tangent of the material,while the storage term is called capacitance. Measuring these propertiesis accomplished by sensing the change of phase and amplitude of anelectric field generated by the instrument and caused by the aggregatedproperties of a body within the field.

FIG. 1 illustrates a system 100 for detecting and analyzing changes in abody according to certain embodiments of the present disclosure. Thesystem 100 includes an external sensor device 102, an electric fieldgenerator 104, an amplitude reference source 106, a quadrature modulator108, an amplitude comparison switch 110, a low pass filter 114, a signalprocessor 116, and a display 118. The components included in the system100 can be further broken down into more than one component and/orcombined together in any suitable arrangement. Further, one or morecomponents can be rearranged, changed, added, and/or removed. In someembodiments, one or more components of the system 100 can be made by anapplication specific integrated circuit (ASIC).

The electric field generator 104 creates an electric field thatilluminates the desired area of detection. The frequency and amplitudeof this electric field is determined by the characteristics of the bodybeing observed. In some embodiments, a frequency-determining componentof the electric field generator 104—a resonant circuit than cancomprised of a combination of inductive, capacitive, and resistiveelements—is connected to an external device that creates the electricfield providing the desired coverage of the body of material beingstudied. In some embodiments, the electric field generator 104 can be anoscillator, such as an inductor-capacitor (LC) tank oscillator.

The external sensor device 102 may be made from a wide variety ofmaterials; the only requirement of these materials is that they areelectrical conductors. The external sensor device 102 can be constructedin many different mechanical configurations to provide appropriatecoverage of the desired region. For example, in some embodiments, theexternal sensor device 102 can be a plurality of metallic plates. Insome embodiments, the shape and/or the orientation of the externalsensor device 102 can be changed as needed.

In some embodiments, the external sensor device 102 is not required tophysically contact the body being studied. For example, the externalsensor device 102 and the supporting electronics could be installed inthe driver's seat of an over-the-highway truck to detect changes inphysiological indicators of driver drowsiness and thus take actions toprevent an accident. In some embodiments, the sensing process usually isdone separately in two paths: (1) in a first path the changes in thereal component of the vector sum, e.g., energy dissipation, aredetected; (2) in a second path the changes related to the imaginarycomponent—a component such as a capacitance or inductance in which thephase of the current flowing in them is orthogonal to the current in thereal component—are separately processed. In some embodiments, thechanges in amplitude of the electric field are detected in the firstpath, and the changes in frequency of the electric field are detected inthe second path. Generally, as known by a person skilled in the art, thechanges in phase of the electric field can be obtained by analyzing thechanges in frequency of the electric field. These two signals can becombined in later signal processing to re-create the changes in thecomplex permittivity or kept as individual signals for separateanalysis. These two paths are discussed separately below.

To detect changes in the imaginary component of the complexpermittivity, the output of the electric field generator 104 isconnected to the quadrature demodulator 108. The quadrature demodulator108 detects the changes of the frequency of the output of the electricfield generator 104 and produce a detected response that includes a lowfrequency component and a high frequency component. FIG. 6 illustrates aquadrature demodulator 108 according to certain embodiments of thepresent disclosure. The quadrature demodulator 108 includes a mixer 602and a resonant circuit 604. In the present disclosure, a double balancedmixer is described, but other suitable types of mixers can also be used.The components included in the quadrature demodulator 108 can be furtherbroken down into more than one component and/or combined together in anysuitable arrangement. Further, one or more components can be rearranged,changed, added, and/or removed.

An input signal to the quadrature demodulator 108 is split into twopaths. One path is connected to one input port of the double balancedmixer 602, and the other path is connected to the resonant circuit 604.The output of the resonant circuit 604 is connected to the other inputport of the double balanced mixer 602. In some embodiments, the resonantcircuit 604 includes an inductor and a capacitor. In some embodiments,the resonant circuit 604 includes an inductor, a capacitor, and aresistor. The circuit components of the resonant circuit 604 can beconnected in series, in parallel, or any other suitable configuration.The resonant circuit 604 can also be implemented by other circuitconfigurations that are appreciated by a person skilled in the art. Insome embodiments, the resonant circuit 604 is tuned to the nominalcenter frequency of the electric field generator 104.

The double balanced mixer 602 multiplies the two signals together (onesignal from the input and the other signal from the resonant circuit604). The product of the two signals creates two components in theoutput: one proportional to the difference between the two inputfrequencies and another at the sum of the two input frequencies. Whenthere is an exact 90-degree phase difference between the two signals,the demodulator output is zero. When the phase difference is less thanabout +/−90 degrees there will be a DC component in the output of thedouble balanced mixer 602.

The output signal from the quadrature demodulator 108 is fed to a lowpass filter 114. The low pass filter 114 is typically an analog circuitthat includes resistive, inductive and/or capacitive elements thatseparates the low frequency component of the quadrature modulator 108from the much higher frequency component generated by the quadraturemodulator 108. The cutoff frequency of the low pass filter is selectedto provide low attenuation of the desired signal components whilesufficiently suppressing the high frequency terms. After filtering, thesignal is connected to the signal processor unit 116 described below.

Detecting changes in electric field dissipation is processed somewhatdifferent from detecting frequency changes in electric field. In FIGS. 1and 6, the output of the electric field generator 104 is multiplied by aphase-shifted version of itself produced by the resonant circuit 604.Unlike phase/frequency change detection, amplitude variations must becompared with the electric field generator 104 output unchanged by thematerial being studied. Referring again to FIG. 1, an amplitudereference signal is created by measuring the output of the electricfield generator 104 in the absence of any external influence and used toset the output level of the amplitude reference source 106.

The amplitude reference source 106 is typically a time and temperaturestable voltage reference that can be provided by a semiconductorcomponent such as a diode. The output of the amplitude reference source106 is fed to one input of the amplitude comparison switch 110. Theswitch 110, controlled by the signal processor 116, alternately connectsthe amplitude reference source 106 and electric field generator output104 to the signal processor 116. By measuring the difference between thereference signal 106 and the electric field generator 104 output—andwith sufficient calibration information—the amount of power absorbed,e.g., dissipated, by the material under study may be computed.

The amplitude comparison switch 110 functions by sampling the output ofthe electric field generator 104 at a rate at least twice as fast as themost rapid variation of the amplitude of the electric field generator104 and subtracting the value of the amplitude reference source 106. Theoutput of the amplitude comparison switch 110 is thus equal to thedifference between the amplitude of the electric field generator 104 andthe amplitude of the amplitude reference source 106.

The signal processor 116 takes the output of the low pass filter 114 andextracts the desired components into desired formats for further use orprocessing. The signal processor 116 also takes the output of theamplitude comparison switch 110 to analyze the changes in amplitude ofthe electric field. The signal processor 116 can be implemented by useof either analog, digital, or combined circuits.

FIG. 7 illustrates a signal processor 116 according to certainembodiments of the present disclosure. The signal processor 116 includesa sample-and-hold circuit 702, an analog-to-digital converter (ADC) 704,a digital signal processor 706, and a microcontroller 708. Thecomponents included in the signal processor 116 can be further brokendown into more than one component and/or combined together in anysuitable arrangement. Further, one or more components can be rearranged,changed, added, and/or removed.

The sample-and-hold circuit 702 is configured to sample acontinuous-time continuous-value signal and hold the value for aspecified period of time. A typical sample-and-hold circuit 702 includesa capacitor, one or more switches, and one or more operationalamplifier. In some embodiments, other suitable circuit implementationscan also be used.

The ADC 704 receives the output of the sample-and-hold circuit 702 andconverts it into digital signals. In some embodiments, the ADC 410 canhave a high resolution. Since the changes in bulk permittivity of theentire region within the electric field in many possible applicationsare expected to be relatively slow, e.g., less than a few hundred Hertz,in some embodiments it can be sufficient to undersample the output ofthe electric field generator 404 by using the sample-and-hold device 406to make short samples that can be processed with the ADC 704 with asample rate in the five thousand samples/sec range. An ADC with 24-bitresolution or 32-bit resolution are readily available. In someembodiments, the ADC 704 can have other suitable resolutions.

The digital signal processor 706 can be configured process the output ofthe ADC 704. In some embodiments, the digital signal processor 706 canbe a microprocessor.

The microcontroller 708 can be coupled to one or more components of thesignal processor 116. In some embodiments, the microcontroller 708 cancontrol the sampling rate and/or clock rate of the one or morecomponents of the signal processor 116. In some embodiments, themicrocontroller 708 can issue command signals to the one or morecomponents of the signal processor 116. In some embodiments, themicrocontroller 708 can be a generic high performance low power systemon chip (SOC) product. For example, the microcontroller 708 can be anARM based processor, such as an ARM Cortex-M4 core processor or anyother suitable models.

Referring to the display 118, the display 118 can be configured todisplay various results generated by the signal processor 116. Thedisplay 118 can be a touch screen, an LCD screen, and/or any othersuitable display screen or combination of display screens. In someembodiments, the output of the signal processor 116 can also be fed to adata logger for signal storage and/or processing.

FIG. 2 shows a generalized version of the transfer function of aquadrature demodulator 108 showing the typical relationship between thevoltage output and frequency of the input signal from the electric fieldgenerator 104. The horizontal axis shows frequency of the input signalin Hertz (Hz), and the vertical axis shows demodulator output in Volts(V). The center of the horizontal axis 210 indicates the nominalresonant frequency of the resonant circuit 604. For example, if thenominal resonant frequency of the resonant circuit 604 is 80 MHz, thenthe center of the horizontal axis 210 is at 80 MHz. The slope of thecentral region 202 of the curve can be made quite linear to allowoperation over an extended frequency range while offering the samesensitivity in terms of output voltage as function of phase/frequencychange. The transfer function is mathematically dependent only on thefrequency/phase relationship between the two inputs to thedouble-balanced mixer 108. This permits a wide and dynamic range indetection in the phase/frequency changes induced by material propertiesseparate from changes in amplitude due to dissipative properties.

FIG. 2 illustrates the sensor operating as it might be employed in twodifferent applications while using the same electric field generator 104and the quadrature demodulator 108. In Region 1 204, the DCcomponent—dependent on the exact value of the frequency and slope of thetransfer function—might be, for example, −1.5 volts. If there are smallvariations in the frequency of the electric field generator 104, therewill also be small variations in the quadrature demodulator outputvoltage. For the example here the output variations will be centeredabout −1.5 volts. In Region 2 206, the DC term might be, for example,around +1.0 volts. However, since the slope of the transfer function isvery close to being the same in both regions, the small variations willbe centered around 0 volts.

This is an important benefit to the approach taken here. If there are awide variety of materials, each with varying electromagnetic propertieswithin the electric field, the aggregated output of the quadraturedemodulator 108 can have a mean DC level determined by the contributionsof all materials within the electric field region, while stillmaintaining an essentially constant transfer function for small changesin material properties. The small-signal linearity allows signalcomponents from separate constituents of the material being studied tobe linearly combined. Linear combination of the various contributions inthe output waveform can be readily separated in later signal processing.An example of a combined waveform showing both respiration and heartrate (pulse) signals is shown in FIG. 3.

FIG. 3 shows a signal comprised of a large, low frequency, roughlytriangular waveform that might be typical of respiration by a body and asignal often seen in a heart pulse of smaller amplitude, higherfrequency, and more complex waveform. In FIG. 3 the linear addition ofthese two waveforms is shown as the smaller amplitude, higher frequency,more complex heart pulse “riding” on the larger, slower triangularrespiration component.

In addition to the largely analog design described above, a“direct-to-digital” approach is also possible. FIG. 4 illustrates asystem 400 for detecting and analyzing changes in a body according tocertain embodiments of the present disclosure. The system 400 includesan external sensor device 402, an electric field generator 404, asample-and-hold device 406, a microcontroller 408, an ADC 410, a digitalsignal processor 416, and a display 418. The components included in thesystem 400 can be further broken down into more than one componentand/or combined together in any suitable arrangement. Further, one ormore components can be rearranged, changed, added, and/or removed. Insome embodiments, the components included in FIG. 4 are similar to thecorresponding components described in FIG. 1 and/or FIG. 7.

In some embodiments, the system 400 replaces most analog componentsdescribed in FIG. 1 with digital or mixed-signal components. The“direct-to-digital” concept employs the ADC 410 driven by thesample-and-hold device 406. In some embodiments, the ADC 410 can have ahigh resolution. Since the changes in bulk permittivity of the entireregion within the electric field in many possible applications areexpected to be relatively slow, e.g., less than a few hundred Hertz, itcan be sufficient to undersample the output of the electric fieldgenerator 404 by using the sample-and-hold device 406 to make shortsamples that can be processed with the ADC 410 with a sample rate in thefive thousand samples/sec range. Such devices with 24-bit resolution arereadily available, as are 32-bit versions at a significantly highercomponent price. In such a system, the signal processor 416 would takeover the functions performed by the quadrature demodulator 108 describedin FIG. 1. Since the features of the “direct-to-digital” instrumentwould be determined by the software in the signal processor 416, asingle hardware set could be loaded with specialized software fordifferent applications. The programmable characteristics of a“direct-to-digital” approach could enable economies of scale, drivingdown the unit cost and opening new market opportunities. In someembodiments, the ADC can be made by an application specific integratedcircuit (ASIC).

FIG. 5 is a flow chart illustrating a process 500 of detecting andanalyzing changes in a body according to certain embodiments of thepresent disclosure. The process 500 is illustrated in connection withthe system 100 shown in FIG. 1 and/or the system 400 shown in FIG. 4. Insome embodiments, the process 500 can be modified by, for example,having steps rearranged, changed, added, and/or removed.

At step 502, an electric field is established around the desired area ofdetection. The desired area of detection is typically around a body thatis going to be monitored. In some embodiments, the electrical field isestablished by using the electric field generator 104, which creates anelectric field that illuminates the desired area of detection. Theprocess 500 then proceeds to step 504.

At step 504, the frequency and amplitude of the electric field of thedesired area of detection are monitored. In some embodiments, theexternal sensor device 102 is used to monitor the area around and withinthe body. The external sensor device 102 is not required to physicallycontact the body being studied. The process 500 then proceeds to step506.

At step 506, the electric field of the desired area of detection isprocessed and analyzed to detect any change. The process 500 can detectthe change of the electric field in both amplitude and frequency/phase.For example, amplitude variations of the electric field can be comparedwith the electric field generator 104 output unchanged by the materialbeing studied. Referring again to FIG. 1, an amplitude reference signalis created by measuring the output of the electric field generator inthe absence of any external influence and used to set the output levelof the amplitude reference source 106. The output of the amplitudereference source 106 is fed to one input of the amplitude comparisonswitch 110. The switch 110, controlled by the signal processor 116,alternately connects the amplitude reference source 106 and electricfield generator output 106 to the signal processor. By measuring thedifference between the reference signal and the electric field generator104 output—and with sufficient calibration information—the amplitudecomparison response of the electric field can be determined.

The change of the electric field in frequency/phase can be detected andanalyzed by the quadrature demodulator configuration discussed inconnection with FIG. 1 and FIG. 6. For example, in some embodiments, theoutput of the electric field generator 104 is connected to thequadrature demodulator that is configured to detect the changes of thefrequency of the output of the electric field generator 104 and producea detected response that includes a low frequency component and a highfrequency component. The detected response is then fed to a low passfilter 114 that is configured to filter out the high frequency componentof the detected response to generate a filtered response. In someembodiments, once the changes in frequency is detected, the changes inphase can be readily derived by people skilled in the art.

The filtered response and the amplitude comparison response can then besupplied to a signal processor for further analysis.

In some embodiments, the change of the electric field can be analyzedunder the “direct-to-digital” approach described in the system 400 inconnection with FIG. 4. The output of the electric field generator 404can be sampled and held by the sample-and-hold device 406 and digitizedby the ADC 410. The digitized output of the ADC 410 can then be analyzedby the digital signal processor 416. The process 500 then proceeds tostep 508.

At step 508, the electric field can be displayed for visual inspection.In some embodiments, the changes of the electric field can also bedisplayed and recorded. In some embodiments, the changes of the electricfield can be extracted to provide specific bodily function features suchas vascular processes and conditions, respiration processes andconditions, and other body material characteristics that vary withpermittivity.

In some embodiments, the system 100 or the system 400 can include aprocessor, which can include one or more cores and can accommodate oneor more threads to run various applications and modules. The softwarecan run on the processor capable of executing computer instructions orcomputer code. The processor may also be implemented in hardware usingan application specific integrated circuit (ASIC), programmable logicarray (PLA), field programmable gate array (FPGA), or any otherintegrated circuit.

The processor can be couple with a memory device, which can be anon-transitory computer readable medium, flash memory, a magnetic diskdrive, an optical drive, a PROM, a ROM, or any other memory orcombination of memories.

The processor can be configured to run a module stored in the memorythat is configured to cause the processor to perform various steps thatare discussed in the disclosed subject matter.

In some embodiments, the electric field generator of the presentinvention has a tuner for adjusting the signal outputting to thequadrature demodulator. In some embodiments, the tuner can beimplemented in an application-specific integrated circuit (ASIC),programmable logic array (PLA), field programmable gate array (FPGA), orany other integrated circuit. In some embodiments, the tuner can beimplemented as a stand-alone subunit connected within or to the electricfield generator. For example, the tuner can be an integratedinductor-capacitor (LC) tank oscillator.

Referring back to FIG. 2, a typical transfer function of a quadraturedemodulator 108 depicts the relationship between the voltage output andfrequency of the input signal from the electric field generator 104. Thehorizontal axis shows the frequency of the input signal in Hertz (Hz),and the vertical axis shows the demodulator output in Volts (V). Thecenter of the horizontal axis 210 indicates the nominal resonantfrequency of a resonant circuit. The slope of the central region 202illustrates the linear frequency range of the electric field generatedby the electric field generator. It may be sometimes desirable, or evennecessary, to expand the linear frequency range of slope 202 in order toallow signal components from separate constituents of a material to belinearly combined. An advantage of linearly combining the variouscontributions is that the output waveform can be readily separated inlater signal processing for individual analysis. In contrast, a signalcomponent not in the linear frequency range cannot be linearly combined,and thus makes it challenging to analyze its individual contribution inthe output waveform.

One of the ways to expand the linear frequency range of the quadraturedemodulator is by adjusting the response curve of the quadraturedemodulator. Such adjustment is possible because the quadraturedemodulator's output voltage is related to the change of the oscillatorfrequency. However, adjusting the quadrature demodulator's output coulddecrease the sensitivity of the system. Alternatively, since thequadrature demodulator's output is a function of the change in frequencyand not the actual frequency, shifting the actual frequency itselfprovides another way to expand quadrature demodulator's linear frequencyrange without sacrificing the sensitivity. For example, FIG. 8illustrates a system 800 for detecting and analyzing changes in a bodyaccording to certain embodiments of the invention. The system 800 iscapable of adjusting the quadrature demodulator's linear frequency rangeby tuning the electric field generator.

Referring to FIG. 8, the system 800 includes an external sensor device802, an electric field generator 804 with a tuner 820, an amplitudereference source 806, a controller 808 with an adjuster 818, aquadrature modulator 810, an amplitude comparison switch 812, a low passfilter 814, and a signal processor 816 configured to output data to adisplay. The components included in the system 800 can be further brokendown into more than one component and/or combined together in anysuitable arrangement. Further, one or more components can be rearranged,changed, added, and/or removed. For example, in some embodiments, system800 can detect and analyze physical changes in an object without theamplitude reference source 806, and amplitude comparison switch 812. Insome embodiments, the system 800 establishes amplitude and/or frequencyreference comparison using a specific feedback value.

In some embodiments, the electric field generator 804 is configured togenerate an electric field based on the information received from theexternal sensor device 802 subject to adjustments made by the tuner 820.The external sensor device 802, connected to the field generator 804, isconfigured to detect physical changes in a body or an object in theelectric field, and to output the sensor information to the electricfield generator 804. The external sensor device 802 may be made from awide variety of materials; the only requirement of these materials isthat they are electrical conductors. To detect the imaginary componentof the changes in the electric field, the output of the electric fieldgenerator 804 is connected to the quadrature demodulator 810. Thequadrature demodulator 810 detects the changes of the frequency of theelectric field and produces a detected response that includes a lowfrequency component and a high frequency component. In some embodiments,the detected response is fed to a low pass filter 814, and then send tothe signal processor 816 for further analysis, similar to the processdepicted in FIG. 1.

In some embodiments, the detected response from the quadraturedemodulator 810 is fed to the controller 808 to establish a feedbackloop for tuning the electric generator 804. The controller 808 caninclude one or more hardware processors, memory components, electroniccircuits, and the like. For example, the controller 808 may include anASIC. The controller 808 can include standalone components, componentsintegrated with other features of system 800, or a combination thereof.In some embodiments, the controller 808 includes the adjuster 818 thatis coupled to the tuner 820 of the electric field generator 804 toenable the system or a user to adjust the outputting signal of theelectric field generator 804.

Referring to FIG. 8, the controller 808 may output a frequency controlsignal, via the adjuster 818, to the tuner 820 of the electric fieldgenerator 804 based on the detected response received from thequadrature demodulator 810. For example, if the detected response showsthat a signal component from a constituent of a material is outside ofthe linear frequency range, the controller 808 can analyze the transferfunction, and output a frequency control signal to the electric fieldgenerator 804 to adjust the electric field generator 804's outputsignal. In some embodiments, the actual frequency of the electric fieldis modified via the frequency control signal. In response, thequadrature the linear frequency range of the quadrature demodulator 810may be expanded so that all signal components are within the linearfrequency range. Although the feedback loop described here is based onthe detected response form the quadrature demodulator 810, responsesfrom other components in the system 800 may also be used. For instance,the feedback loop can also be established via the filtered response fromthe low pass filter 814, the analyzed response from the signal processor816, or directly from the output of the electric field generator 804. Insome embodiments, the feedback loop can receive signals from more thanone component of the system 800.

The frequency control signal may be transmitted via any suitablecommunication media, including wired or wireless media. In someembodiments, the frequency control signal may include one or more analogelectrical signals, digital electrical signals, electrical waveforms(e.g., pulse-width modulation waveforms), or the like.

In some embodiments, the electric field generator 804 includescomponents with different functions. For example, the electric fieldgenerator 804 can include an LC tank oscillator, a buffer, and a powerconditioning element. In some embodiments, the LC tank oscillator isconfigured as a Colpitts oscillator or any other suitable oscillator;the buffer is a unity gain device that shields the LC tank oscillatorfrom undesired interactions with the quadrature demodulator 810; and thepower condition element insures a stable power value for the LC tankoscillator and the buffer. The Colpitts oscillator can be the electricfield generator 804's tuner 820. In operation, the controller 808 maysend a frequency control signal to adjust the values of the inductor (L)and/or capacitor (C) of the Colpitts oscillator such that the signalentering the quadrature modulator 810 will always be within the linearlimits of the quadrature demodulator 810's linear frequency range.Different types of variable inductor or capacitor may be used in theColpitts oscillator. In some embodiments, the values of the L and C canbe adjusted by combining the fixed values of L and of C with one or moreof electrically sensitive inductive and/or capacitive components. Hence,by altering the electricity flowing through at least one of theelectrically sensitive inductive or capacitive components, thecontroller 808 can effectively change the values of L or C, and thusmodify the signal entering the quadrature modulator 810. In someembodiments, the flow of electricity is controlled by manually adjustingan electric source. In some embodiments, the flow of electricity can beautomatically controlled by a voltage circuit.

FIG. 9 illustrates a Colpitts oscillator 900 according to certainembodiments of the invention. The Colpitts oscillator 900 includes twomain components: an amplifier 904 and a resonant tank circuit 906.Colpitts oscillators are known for their ability to output signals witha fixed frequency. According to certain embodiments, the Colpittsoscillator 900 is initialized when a small input, usually random noise,that is received by the amplifier 904. The amplifier 904 increases themagnitude of the initial small input and sends an amplified signal tothe resonant tank circuit 906 which includes an inductive element 908and a capacitive element 910. The input and output of the resonant tankcircuit 910 are configured to only allow signals to pass through with asingle frequency. Hence, the amplified signal can only enter and exitthe resonant tank circuit 906 with a single frequency. The output of theresonant tank circuit 906 is then fed back to the input of the amplifier904 to via feedback loop. In operation, the feedback process wouldcontinue so long as the amplifier has sufficient gain to overcome anylosses in the resonant tank circuit 906. The feedback process enablesthe Colpitts oscillator to reliability output signals with a fixedfrequency.

According to certain embodiments, the electric field generator 804 withColpitts oscillator as its tuner can be tuned by a frequency controlsignal from the controller 808. Specifically, the frequency ofoscillation, measured in Hertz, is defined by

$\frac{1}{\sqrt{LC}},$

where L is the inductive component measured in Henries and C is thecapacitive component measured in Farads. Referring to FIG. 9, to tunethe electric field generator 804, the frequency control signal wouldadjust the value of the inductive 908 and capacitive component 910 inthe resonant tank circuit 906. In some embodiments, the inductive andcapacitive components can be combined with multiple constituents. Forexample, the inductive component 908 may be a single device of fixedinductance while the capacitive component 910 might be implemented astwo separate devices—one with a fixed value and the other a variablecapacitor. As another example, the capacitive component 910 may be asingle device of fixed capacitance while the inductive component 908might be implemented as two separate devices—one with a fixed value andthe other as a variable inductor. In some embodiments, the variablecapacitor may be a varactor—a type of diode which changes capacitancewith voltage application. However, other variable capacitors that canchange the capacitance with application of voltage are also within thescope of the invention. In some embodiments, the variable inductor maybe a microelectromechanical system (MEMS) variable inductor. However,other variable inductors that can change the inductance with applicationof voltage are also within the scope of the invention.

As mentioned above, in some embodiments the system 800 can automaticallytune the frequency of the electric field generated via a feedback loop.For example, the controller 808 may send the frequency control signalbased on a voltage received from the quadrature demodulator 810. Inother embodiments, the controller 808 may send the frequency controlsignal based on one or more voltages received from the low pass filter814, the signal processor 816, the electric field generator 801, and/orother components of the system 800.

In some embodiments, the controller 808 can tune the electric fieldgenerator 804 without receive any response from the quadraturedemodulator 810, the low pass filter 814, the signal processor 816, orother components of the system 800. An operator may manually adjust theknobs on the controller to tune the LC tank oscillator based on his orher observation of the data from any components in system 800. Othermanual adjustment techniques and mechanisms are also within the scope ofthe invention.

In some embodiments, the controller 808 can sample the detected responsefrom the quadrature modulator 810 to determine other changes in thefrequency not caused by the LC tank oscillator. In this regard, thecontroller 808 can hold the variable components of the LC tankoscillator constant, and act as a monitoring system for detecting otherfrequency changing variables. For example, the controller 808 may pickup frequency changes caused by the external sensor device 802. In someembodiments, the monitored information can be fed directly to the signalprocessor 816 for analysis or for outputting to an external display.

FIG. 10 is a flow chart illustrating a process 1000 of detecting andanalyzing changes in a body according to certain embodiments of thepresent disclosure. The process 1000 is illustrated in connection withthe system 800 shown in FIG. 8. In some embodiments, the process 1000can be modified by, for example, having steps rearranged, changed,added, and/or removed.

At step 1002, an electric field associated with the body is generated.The body need not be the whole body, it can be a specific part of thebody. In some embodiments, the electrical field is generated by usingthe electric field generator 804, which creates an electric field thatilluminates a desired area of detection. The process 1000 then proceedsto step 1004.

At step 1004, a physical change in the body is detected in the electricfield generated in step 1002. In some embodiments, the external sensordevice 802 is used to monitor the area around and within the body. Theexternal sensor device 802 is not required to physically contact thebody being studied. The process 1000 then proceeds to step 1006.

At step 1006, changes in the frequency of the electric field is detectedand monitored, and a detected response is produced. In some embodiments,the quadrature modulator 806 is used to monitor and detect the frequencychange of the electric field. Referring to FIG. 8, in some embodiments,frequency changes are reflected in the transfer function of thequadrature demodulator 806, where the transfer function shows therelationship between the voltage output and the frequency of the inputsignal from the electric field generator 804. In some embodiments, thedetected response is subsequently send to one or more other componentsfor further analysis or processing. In some embodiments, the detectedresponse is sent to a component not depicted in FIG. 8. In someembodiments, the detected response is sent to the controller 808. Insome embodiments, the detected response is initially sent to anothercomponent such as the low pass filter 814, before passing on to thecontroller 808. The process 1000 then proceeds to step 1008.

At step 1008, a frequency control signal is outputted to a component formodifying the frequency of the electric field. In some embodiments, theadjuster 818 of the controller 808 is used to output the frequencycontrol signal. And the electric field generator 804 is used to receivethe frequency control signal. Referring back to FIG. 8, although in someembodiments the output of the controller 808 is fed directly to theinput of the electric field generator 804, other communication paths arealso possible. For example, the frequency control signal can be routedto another component not depicted in FIG. 8 before arriving at theelectric field generator 804. In some embodiments, the frequency controlsignal is received by the tuner 820 of the electric field generator 804.In some embodiments, the frequency control signal is received by anothercomponent or circuit within the electric field generator 804 (not shownin FIG. 8). The process 1000 then proceeds to step 1010.

At step 1010, an electric field generated by the electric fieldgenerator is modified based on the frequency control signal. In someembodiments, the electric field being modified is the electric fieldgenerated in step 1002. In some embodiments, the electric field beingmodified is another electric field generated after step 1002. Accordingto certain embodiments, the tuner 820 modifies the electric field basedon the frequency control signal. In some embodiments, another componentor circuit within the electric field generator (not shown) can modifythe electric field based on the frequency control signal. In someembodiments, another component, not necessary in the system 800, canreceive the frequency control signal and modify the electric fieldaccordingly. In some embodiments, the process 1000 ends at step 1010. Insome embodiments, the system 800 repeats the process 1000 multiple timesto achieve a proper adjustment.

The following applications and/or methods are non-limiting examples ofapplying the disclosed subject matter.

In some embodiments, changes in capacitor excitation frequency can beremotely sensed to alleviate the need for analog data reduction at thesensor.

In some embodiments, blood pressure can be measured by isolating a bodyregion using a pressure “doughnut” and then releasing pressure andmonitoring the return of blood flow as a result. Traditional meansenclosing a limb to close an artery and monitor the pressure at whichthe artery opens up as the pressure is released. With the disclosedinvention, a body region can be determined that excludes blood byclosing capillaries (within the ‘doughnut’ pressure region) andmonitoring the pressure at which they then open again. Thissimplification of application could then be applied to in-seatcircumstances in hospital/clinic waiting rooms and the like.

In some embodiments, first derivatives can be used to find a recurringpattern in a combined time series signal of heartbeat and respirationsuch that the respiration signal can be subtracted from the combinedsignal to leave the heartbeat signal.

In some embodiments, the mathematical notion of Entropy (H) can be usedto analyze a heartbeat signal and extract event timing information withrespect to characterizing heart processes.

In some embodiments, wavelet analysis can be used to disambiguatecomplex time series data with highly variable frequency compositions.Signals that vary their frequency in time are resistant to effectiveanalysis using traditional digital techniques such as fast Fouriertransform (FFT). Wavelets provide the notion of short patterncorrelation that can be applied to a sliding window of time series datain order to provide a second correlation time series that indicates thetime at which a test pattern or “wavelet” is found within the first timeseries.

In some embodiments, a low resolution FFT can be used to peak search forpower levels in a correlation function. This FFT power analysis is thenused to set the correlation cutoff level and thus determine higherresolution correlated frequencies based on the power levels provides bythe FFT. The FFT essentially filters out correlations below a particularpower level so that more strongly correlated signals can remain. Thisprovides a way of efficiently ‘normalizing’ the power levels relative toone another in trying to separate low frequency signals that arerelatively close in frequency but widely separated in power withouthaving to increase the resolution of the FFT with attendantsignificantly increased FFT window acquisition time.

In some embodiments, Kalman filters can be used to process the effect ofchanges in permittivity as indicated by a time series data such that thefilter relates the predicted next value in a time series in maintaininga useable moving average for the purposes of normalizing a highlyvariable signal from a sensor with high dynamic range.

In some embodiments, measurement of the temperature of a body orsubstance can be obtained by measuring the permittivity of said body orsubstance where such permittivity may be correlated to temperature.

In some embodiments, measurement of the pressure within a body,substance, and/or liquid can be obtained by measuring the permittivityof said body, substance, and/or liquid where such permittivity may becorrelated to pressure.

In some embodiments, stress levels in an individual can be determined byanalyzing his or her motion, heartbeat characteristics and respirationusing a remote, non-contact, biometric sensor.

In some embodiments, the quality of food in food processing and handlingoperations can be monitored by correlating the qualities of the food tothe measured permittivity of the food item.

In some embodiments, the characteristics (e.g., turbulence, flow,density, temperature) of a fluid (e.g., paint, blood, reagents,petroleum products) can be monitored by correlating the characteristicsof the fluid to the objective characteristics of the fluid.

In some embodiments, cavities and/or impurities in solid materials canbe found. Such application can be used in areas such as the detection ofdelamination in composite materials, voids in construction materials,entrained contaminants, and/or the quality of fluid mixing.

In some embodiments, contraband enclosed within solid objects can befound.

In some embodiments, the life signs of infants in cribs, pushchairsand/or car seats can be monitored.

In some embodiments, the presence and life signs located in automobilescan be detected for the purposes of providing increased passengersafety, deploying airbags, and/or prevent baby from being left behind.

In some embodiments, the sentience of a driver can be detected by usingheartbeat variability. In some embodiments, gestures such as thehead-nod signature motion.

In some embodiments, the life signs in unauthorized locations (e.g.,smuggling and/or trafficking) can be discovered.

In some embodiments, the quality of glass manufacture can be assessed bydetecting variations in thickness, poor mixing, and/or the entrainmentof impurities and/or.

In some embodiments, the nature of underground/sub-surface texture andinfrastructure (pipes and similar) can be assessed.

In some embodiments, the external sensor device disclosed herein can becombined with other sensors (e.g., camera, echolocation,pressure/weight/accelerometers) to provide enhanced sensor applicationusing sensor “fusion.”

In some embodiments, certain body conditions can be detected. The bodyconditions include conditions of the body relating to heart-lungfunctions, pulmonary fluid levels, blood flow and function, large andsmall intestine condition and process, bladder condition (full/empty)and process (rate fill/empty), edema and related fluid conditions, bonedensity measurement, and any other suitable condition or combination ofconditions.

It is to be understood that the disclosed subject matter is not limitedin its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The disclosed subject matter is capable ofother embodiments and of being practiced and carried out in variousways. Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of description and should not beregarded as limiting.

As such, those skilled in the art will appreciate that the conception,upon which this disclosure is based, may readily be utilized as a basisfor the designing of other structures, systems, methods, and media forcarrying out the several purposes of the disclosed subject matter.

Although the disclosed subject matter has been described and illustratedin the foregoing exemplary embodiments, it is understood that thepresent disclosure has been made only by way of example, and thatnumerous changes in the details of implementation of the disclosedsubject matter may be made without departing from the spirit and scopeof the disclosed subject matter.

What is claimed:
 1. A system for detecting and analyzing a change in abody, comprising: an electric field generator configured to generate anelectric field that associates with the body; an external sensor devicethat sends information to the electric field generator, configured todetect a physical change in the body in the electric field, wherein thephysical change causes a frequency change of the electric field; aquadrature demodulator that receives the electric field from theelectric field generator, configured to detect the frequency change ofthe electric field generated by the electric field generator and toproduce a detected response; and a controller, coupled to the electricfield generator, configured to output a frequency control signal to theelectric field generator and to modify the frequency of the electricfield by adjusting the frequency control signal.
 2. The system of claim1, wherein the modified frequency of the electric field is within alinear frequency range of the quadrature demodulator.
 3. The system ofclaim 1, wherein the controller is further configured to change thefrequency control signal based on a feedback response.
 4. The system ofclaim 3, wherein the feedback response is the detected response from thequadrature demodulator.
 5. The system of claim 1, wherein the electricfield generator comprises an oscillator.
 6. The system of claim 5,wherein the oscillator is an inductor-capacitor tank oscillator.
 7. Thesystem of claim 6, wherein the inductor-capacitor tank oscillatorcomprises at least one of a variable inductor or a variable capacitor.8. The system of claim 7, wherein the at least one of the variableinductor or the variable capacitor is configured to modify the frequencyof the electric field according to a tuning signal produced by thefrequency control signal.
 9. The system of claim 1, further comprising:a low pass filter that receives information from the quadraturedemodulator, wherein the detected response produced by the quadraturedemodulator includes a low frequency component and a high frequencycomponent, and wherein the low pass filter is configured to filter outthe high frequency component of the detected response to generate afiltered response.
 10. The system of claim 9, wherein the controller isfurther configured to change the frequency control signal based on afeedback response.
 11. The system of claim 10, wherein the feedbackresponse is the filtered response from the low pass filter.
 12. Thesystem of claim 9, further comprising: a signal processor that receivesinformation from the low pass filter, analyzes the filtered response,and outputs an analyzed response.
 13. The system of claim 12, furthercomprising: an amplitude reference source configured to provide anamplitude reference; and an amplitude comparison switch that receivesamplitude information from the amplitude reference source and theelectric field generator, configured to compare the amplitude referenceand the amplitude of the electric field to generate an amplitudecomparison, wherein the signal processor is further configured toreceive information from the amplitude comparison switch and to analyzethe amplitude comparison.
 14. The system of claim 12, wherein thecontroller is further configured to change the frequency control signalbased on the analyzed response from the signal processor.
 15. The systemof claim 1, wherein the controller is further configured to monitor thedetected response from the quadrature demodulator, and to send an outputsignal to a signal processor.
 16. The system of claim 1, furthercomprising: a low pass filter that receives the detected response fromthe quadrature demodulator and produces a filtered response, wherein thecontroller is further configured to monitor the filtered response, andto send an output signal to a signal processor.
 17. The system of claim15, wherein the controller is further configured to instruct theelectric field generator to hold the frequency of the electric fieldconstant, and to determine other frequency changing variables via thedetected response.
 18. The system of claim 15, wherein the signalprocessor is configured to analyze the output signal.
 19. A method fordetecting and analyzing changes in a body, the method comprising:generating, by an electric field generator, an electric field thatassociates with the body; detecting, by an external sensor device, aphysical change in the body in the electric field, wherein the physicalchange affects frequency of the electric field; monitoring anddetecting, by a quadrature demodulator, changes in the frequency of theelectric field and producing a detected response with at least afrequency component; receiving, by a controller, the detected responsewith at least a frequency component; outputting, by the controller, afrequency control signal to modify the frequency of the electric fieldassociated with the body; and modifying, by the electric fieldgenerator, the electric field associated with the body based on thefrequency control signal.
 20. A non-transitory computer readable mediumstoring executable instructions operable for detecting and analyzing achange in a body to cause a processor to perform operations comprising:generating, by an electric field generator, an electric field thatassociates with the body; detecting, by an external sensor device, aphysical change in the body in the electric field, wherein the physicalchange affects frequency of the electric field; monitoring anddetecting, by a quadrature demodulator, changes in the frequency of theelectrical field and producing a detected response with at least afrequency component; receiving, by a controller, the detected responsewith at least a frequency component; outputting, by the controller, afrequency control signal to modify the frequency of the electric fieldassociated with the body; and modifying, by the electric fieldgenerator, the electric field associated with the body based on thefrequency control signal.